The world at the beginning of the century

In Europe, the British Empire achieved the height of its power. Germany and Italy, which came into existence as unified nations at the end of the 19th century, grew in power, challenging the traditional hegemony of Britain and France. With nationalism in full force at this time, the European powers competed with each other for land, military strength and economic power.

Asia and Africa were for the most part still under control of their European colonizers. The major exceptions were China and Japan. The Russo-Japanese War in 1905 was the first major instance of a European power being defeated by a so-called inferior nation. The war itself strengthened Japanese militarism and enhanced Japan's rise to the status of a world power. Tsarist Russia, on the other hand, did not handle the defeat well. The war exposed the country's military weakness and increasing economic backwardness, and contributed to the Russian Revolution of 1905, the dress rehearsal for the conclusive one in 1917.

Already in the 19th century, the United States had become an influential actor in world politics. It had made its presence known on the world stage by challenging Spain in the Spanish-American War, gaining the colonies of Puerto Rico and the Philippines as protectorates. Now, with growth in immigration and a resolution of the national unity issue through the bloody American Civil War, America was emerging as an industrial power as well, rivaling Britain, Germany, and France.

With increasing rivalry among the European powers, and the rise of Japan and the United States, the stage was set for a major upheaval in world affairs.

"The war to end all wars": World War I (1914–1918)

The First World War, termed "The Great War" (or simply WWI) by contemporaries, started in 1914 and ended in 1918. It was ignited by the Assassination in Sarajevo of the Austro-Hungarian Empire's heir to the throne, Erzherzog Franz Ferdinand, by Gavrilo Princip of the Serbian nationalist organization "Black Hand". Bound by Slavic nationalism to help the small Serbian state, the Russians came to the aid of the Serbs when they were attacked. Interwoven alliances, an increasing arms race, and old hatreds dragged Europe into war. The Allies, known initially as "The Triple Entente", comprised the British Empire, Russia and France, as well as Italy and the United States later in the war. On the other side, Germany, along with Austria-Hungary , Bulgaria and later the Ottoman Empire, were known as "The Central Powers".

In 1917, Russia ended hostile actions against the Central Powers after the fall of the Tsar. The Bolsheviks negotiated the Treaty of Brest-Litovsk with Germany, although it was at huge cost to Russia. Although Germany shifted huge forces from the eastern to the western front after signing the treaty, it was unable to stop the Allied advance, especially with the entrance of American troops in 1918.

The war itself was also a chance for the combatant nations to show off their military strength and technological ingenuity. The Germans introduced the machine gun, U-Boats and deadly gases. The British first used the tank. Both sides had a chance to test out their new aircraft to see if they could be used in warfare. It was widely believed that the war would be short. Unfortunately, since trench warfare was the best form of defense, advances on both sides were very slow, and came at a terrible cost in lives.

When the war was finally over in 1918, the results would set the stage for the next twenty years. First and foremost, the Germans were forced to sign the Treaty of Versailles, forcing them to make exorbitant payments to repair damages caused during the War. Many Germans felt these reparations were unfair because they did not actually "lose" the war nor did they feel they caused the war (see Stab-in-the-back legend). Germany was never occupied by Allied troops, yet it had to accept a liberal democratic government imposed on it by the victors after the abdication of Kaiser Wilhelm.

Much of the map of Europe was redrawn by the victors based upon the theory that future wars could be prevented if all ethnic groups had their own "homeland". New states like Yugoslavia and Czechoslovakia were created out of the former Austro-Hungarian Empire to accommodate the nationalist aspirations of these groups. An international body called the League of Nations was formed to mediate disputes and prevent future wars, although its effectiveness was severely limited by, among other things, its reluctance and inability to act.

The Russian Revolution and communism

The Russian Revolution of 1917 sparked a wave of communist revolutions across Europe, prompting many to believe that a socialistworld revolution could be realized in the near future. However, the European revolutions were defeated, Lenin died in 1924, and within a few years Joseph Stalin displaced Leon Trotsky as the de facto leader of the Soviet Union. The idea of worldwide revolution was no longer in the forefront, as Stalin concentrated on "socialism in one country" and embarked on a bold plan of collectivization and industrialization. The majority of socialists and even many communists became disillusioned with Stalin's autocratic rule, his purges and the assassination of his "enemies", as well as the news of famines he imposed on his own people.

Communism was strengthened as a force in Western democracies when the global economy crashed in 1929 in what became known as the Great Depression. Many people saw this as the first stage of the end of the capitalist system and were attracted to Communism as a solution to the economic crisis, especially as the Soviet Union's economic development in the 1930s was strong, unaffected by the capitalist world's crisis.

Between the wars

Economic depression

After World War I, the global economy remained strong through the 1920s. The war had provided a stimulus for industry and for economic activity in general. There were many warning signs foretelling the collapse of the global economic system in 1929 that were generally not understood by the political leadership of the time. The responses to the crisis often made the situation worse, as millions of people watched their savings become next to worthless and the idea of a steady job with a reasonable income fading away.

Many sought answers in alternative ideologies such as communism and fascism. They believed that the capitalist economic system was collapsing, and that new ideas were required to meet the crisis. The early responses to the crisis were based upon the assumption that the free market would correct itself. This, however, did very little to correct the crisis or to alleviate the suffering of many ordinary people. Thus, the idea that the existing system could be reformed by government intervention in the economy rather than by continuing the laissez-faire approach became prominent as a solution to the crisis. Democratic governments assumed the responsibility to provide needed services in society and alleviate poverty. Thus was born the welfare state. These two politico-economic principles, the belief in government intervention and the welfare state, as opposed to the belief in the free market and private institutions, would define many political battles for the rest of the century.

The rise of dictatorship

Fascism first appeared in Italy with the rise to power of Benito Mussolini in 1922. The ideology was supported by a large proportion of the upper classes as a strong challenge to the threat of communism.

When Adolf Hitler came to power in Germany in 1933, a new variant of fascism called Nazism took over Germany and ended the German experiment with democracy. The National Socialist party in Germany was dedicated to the restoration of German honor and prestige, the unification of German-speaking peoples, and the annexation of Central and Eastern Europe as vassal states, with the Slavic population to act as slave labor to serve German economic interests. There was also a strong appeal to a mythical racial purity (the idea that Germans were the Herrenvolk or the "master race"), and a vicious anti-semitism which promoted the idea of Jews as subhuman (Untermensch) and worthy only of extermination.

Many people in Western Europe and the United States greeted the rise of Hitler with relief or indifference. They could see nothing wrong with a strong Germany ready to take on the communist menace to the east. Anti-semitism during the Great Depression was widespread as many were content to blame the Jews for causing the economic downturn.

Hitler began to put his plan in motion, annexing Austria in the Anschluss, or reunification of Austria to Germany, in 1938. He then negotiated the annexation of the Sudetenland, a German speaking mountainous area of Czechoslovakia, in the Munich Conference. The British were eager to avoid war and believed Hitler's assurance to protect the security of the Czech state. Hitler annexed the rest of the Czech state shortly afterwards. It could no longer be argued that Hitler was solely interested in unifying the German people.

Fascism was not the only form of dictatorship to rise in the post-war period. Almost all of the new democracies in the nations of Eastern Europe collapsed and were replaced by authoritarian regimes. Spain also became a dictatorship under the leadership of General Francisco Franco after the Spanish Civil War. Totalitarian states attempted to achieve total control over their subjects as well as their total loyalty. They held the state above the individual, and were often responsible for some of the worst acts in history, such as the Holocaust Adolf Hitler perpetrated on European Jews, or the Great Purge Stalin perpetrated in the Soviet Union in the 1930s.

Global war: World War II (1939–1945)

The war in Europe

This section provides a conversational overview of World War II in Europe. See main article for a fuller discussion.

Soon after the events in Czechoslovakia, Britain and France issued assurances of protection to Poland, which seemed to be next on Hitler's list. World War II officially began on September 1, 1939. On that date, Hitler unleashed his Blitzkrieg, or lightning war, against Poland. Britain and France, much to Hitler's surprise, immediately declared war upon Germany, but the help they could afford Poland was negligible. After only a few weeks, the Polish forces were overwhelmed, and its government fled to exile in London (see Polish government in Exile).

In starting World War II, the Germans had unleashed a new type of warfare, characterized by highly mobile forces and the use of massed aircraft. The German strategy concentrated upon the devotion of the Wehrmacht, or German army, to the use of tank groups, called panzer divisions, and groups of mobile infantry, in concert with relentless attacks from the air. Encirclement was also a major part of the strategy. This change smashed any expectations that the Second World War would be fought in the trenches like the first.

As Hitler's forces conquered Poland, the Soviet Union, under General Secretary Joseph Stalin, was acting out guarantees of territory under a secret part of a nonaggression pact between the USSR and Germany known as the Nazi-Soviet Pact. This treaty gave Stalin free rein to take the Baltic republics of Estonia, Latvia, and Lithuania, as well as Eastern Poland, all of which would remain in Soviet possession after the war. Stalin also launched an attack on Finland, which he hoped to reduce to little more than a Soviet puppet state, but the Red Army met staunch Finnish resistance in what became known as the Winter War, and succeeded in gaining only limited territory from the Finns. This action would later cause the Finns to ally with Germany when its attack on the Soviet Union came in 1941.

After the defeat of Poland, a period known as the Phony War ensued during the winter of 1939–1940. All of this changed on May 10, 1940, when the Germans launched a massive attack on the Low Countries (Belgium, the Netherlands, and Luxembourg), most probably to surmount the Maginot Line of defenses on the Franco-German border. This witnessed the incredible fall of Eben Emael, a Belgian fort considered impregnable and guarded by 600 Belgians, to a force of only 88 German paratroopers. The worst of this was that King Léopold III of Belgium surrendered to the Germans on May 28 without warning his allies, exposing the entire flank of the Allied forces to German panzer groups. Following the conquest of the Low Countries, Hitler occupied Denmark and Norway, beginning on April 9, 1940. Norway was strategically important because of its sea routes which supplied crucial Swedish ore to the Nazi war machine. Norway held on for a few crucial weeks, but Denmark surrendered after only four days.

With the disaster in the Low Countries, France, considered at the time to have had the finest army in world, lasted only four weeks, with Paris being occupied on June 14. Three days later, Marshal Philippe Pétain surrendered to the Germans. The debacle in France also led to one of the war's greatest mysteries, and Hitler's first great blunder, Dunkirk, where a third of a million trapped British and French soldiers were evacuated by not only British war boats, but every boat the army could find, including fishing rafts. Hitler refused to "risk" his panzers on action at Dunkirk, listening to the advice of Air Minister Hermann Göring and allowing the Luftwaffe, or German Air Force, to handle the job. The irony of this was that the escaped men would form the core of the army that was to invade the beaches of Normandy in 1944. Hitler did not occupy all of France, but about three-quarters, including all of the Atlantic coast, allowing Marshal Pétain to remain as dictator of an area known as Vichy France. However, members of the escaped French Army formed around General Charles de Gaulle to create the Free French forces, which would continue to battle Hitler in the stead of an independent France. At this moment, Italy, under Benito Mussolini, declared war on the Allies on June 10, thinking that the war was almost over, but he managed only to occupy a few hundred yards of French territory. Throughout the war, the Italians would be more of a burden to the Nazis than a boon, and would later cost them precious time in Greece.

Hitler now turned his eyes on Great Britain, which stood alone against him. He ordered his generals to draw up plans for an invasion, code named Operation Sea Lion, and ordered the Luftwaffe to launch a massive air war against the British isles, which would come to be known as the Battle of Britain. The British at first suffered steady losses, but eventually managed to turn the air war against Germany, taking down 2,698 German planes throughout the summer of 1940 to only 915 Royal Air Force (RAF) losses. The key turning point came when the Germans discontinued successful attacks against British airplane factories and radar command and coordination stations and turned to civilian bombing known as terror bombing using the distinctive "bomb" sound created by the German dive-bomber, the Stuka. The switch came after a small British bombing force had attacked Berlin. Hitler was infuriated. However, his decision to switch the attacks' focus allowed the British to rebuild the RAF and eventually force the Germans to indefinitely postpone Sea Lion.

The importance of the Battle of Britain is that it marked the beginning of Hitler's defeat. Secondly, it marked the advent of radar as a major weapon in modern air war. With radar, squadrons of fighters could be quickly assembled to respond to incoming bombers attempting to bomb civilian targets. It also allowed the identification of the type and a guess at the number of incoming enemy aircraft, as well as tracking of friendly airplanes.

Hitler, taken aback by his defeat over the skies of Britain, now turned his gaze eastward to the Soviet Union. Despite having signed the non-aggression pact with Stalin, Hitler despised communism and wished to destroy it in the land of its birth. He originally planned to launch the attack in early spring of 1941 to avoid the disastrous Russian winter. However, a pro-allied coup in Yugoslavia and Mussolini's almost utter defeat in his invasion of Greece from occupied Albania prompted Hitler to launch a personal campaign of revenge in Yugoslavia and to occupy Greece at the same time. The Greeks would have a bitter revenge of sorts; the attack caused a delay of several crucial weeks of the invasion of Russia.

On June 22, 1941, Hitler attacked Stalin with the largest army the world has ever seen. Over three million men and their weapons were put into service against the Soviet Union. Stalin had been warned about the attack, both by other countries and by his own intelligence network, but he had refused to believe it. Therefore, the Russian army was largely unprepared and suffered incredible setbacks in the early part of the war, despite Stalin's orders to counterattack the Germans. Throughout 1941, German forces, divided into 3 army groups (Army Group A, Army Group B, and Army Group C), occupied the Eastern Europe states of Ukraine and Belarus, laid siege to Leningrad (present day Saint Petersburg), and advanced to within 15 miles of Moscow. At this critical moment, the Russian winter, which began early that year, stalled the German Wehrmacht to a halt at the gates of Moscow. Stalin had planned to evacuate the city, and had already moved important government functions, but decided to stay and rally the city. Recently arrived troops from the east under the command of military genius Marshal Georgi Zhukov counterattacked the Germans and drove them from Moscow. The German army then dug in for the winter.

Here marks the third great blunder of Hitler's. He could have won the war in the USSR except for a few reasons. One, he started the war too late to avoid the Russian winter. Second, he tried to capture too much too fast; he wanted the German army to advance all the way to the Urals, which amounted to one million square miles (2,600,000 km²) of territory, when he probably should have concentrated on taking Moscow and thereby driving a wedge into heart of the Soviet Union. Third, he ignored the similar experiences of Napoleon Bonaparte nearly one hundred and fifty years earlier in his attempt to conquer Russia. Despite this, Stalin was not in a good position. Roughly two-fifths of the USSR's industrial might was in German hands. Also, the Germans were at first seen by many as liberators fighting the communists. Stalin was also not a very able general, and like Hitler, at first tried to fight the war as a military strategist. However, Hitler managed to turn all of his advantages against himself, and lost the only remaining hope for Germany: seizing the Caucasus and taking control of North Africa and the oil-rich Middle East.

Mussolini had launched an offensive in North Africa from Italian-controlled Libya into British-controlled Egypt. However, the British smashed the Italians and were on the verge of taking Libya. Hitler decided to help by sending in a few thousand troops, a Luftwaffe division, and the first-rate general Erwin Rommel. Rommel managed to use his small force to repeatedly smash massively superior British forces and to recapture the port city of Tobruk and advance into Egypt. However, Hitler, embroiled in his invasion of the Soviet Union, refused to send Rommel any more troops. If he had, Rommel might have been able to seize the Middle East, where Axis-friendly regimes had taken root in Iraq and Persia (present-day Iran). Here, Rommel could have cut the major supply route of the Soviets through Persia, and helped take the Caucasus, virtually neutralizing Britain's effectiveness in the war and potentially sealing the fate of the USSR. However, Hitler blundered again, throwing away the last vestiges of the German advantage on his coming offensive in 1942.

After the winter, Hitler launched a fresh offensive in the spring of 1942, with the aim of capturing the oil-rich Caucacus and the city of Stalingrad. However, he repeatedly switched his troops to where they were not needed. The offensive bogged down, and the entire 6th Army, considered the best of German troops, was trapped in Stalingrad. Hitler now refused to let 6th Army break out. He insisted that the German army would force its way in. Hermann Goering also assured Hitler that the Luftwaffe could supply the 6th Army adequately, when it could in reality only supply a minute fraction of the needed ammunition and rations. Eventually, the starved 6th Army surrendered, dealing a severe blow to the Germans. In the end, the defeat at Stalingrad was the turning point for the war in the east.

Meanwhile, the Japanese had attacked the United States at Pearl Harbor in Hawaii on December 7, 1941. This disastrous attack forced the Americans into the war. Hitler need not have declared war on the United States, and kept its continued neutrality in Europe, but he did not. Both he and Mussolini declared war only a few days after the attack. At the time, most German generals, preoccupied with war in Russia, did not even notice America's entrance. It was to be a crucial blunder.

Throughout the rest of 1942 and 1943, the Soviets began to gain ground against the Germans. The tank battle of Kursk is one example. However, by this time, Rommel had been forced to abandon North Africa after a defeat by Montgomery at El Alamein, and the Wehrmacht had encountered serious casualties that it could not replace. Hitler also insisted on a "hold at all costs" policy which forbade relinquishing any ground. He followed a "fight to the last man" policy that was completely ineffective. By the beginning of 1944, Hitler had lost all initiative in Russia, and was struggling even to hold back the tide turning against him.

From 1942 to 1944, the United States and Britain acted in only a limited manner in the European theater, much to the chagrin of Stalin. They drove out the Germans in Africa, invading Morocco and Algeria on November 8, 1942. Then, on July 10, 1943, the Allies invaded Sicily, in preparation for an advance through Italy, the "soft underbelly" of the Axis, as Winston Churchill called it. On September 9, the invasion of Italy began. By the winter of 1943, the southern half of Italy was in Allied hands. The Italians, most of whom did not really support the war, had already turned against Mussolini. In July, he had been stripped of power and taken prisoner, though the Italians feigned continued support of the Axis. On September 8, the Italians formally surrendered, but most of Italy not in Allied hands was controlled by German troops and those loyal to Mussolini's (Mussolini had been freed by German paratroopers) new Italian Social Republic, which in reality consisted of the shrinking zone of German control. The Germans offered staunch resistance, but by June 4, 1944, Rome had fallen.

The Second Battle of the Atlantic took place from 1942 to 1944. The Germans hoped to sever the vital supply lines between Britain and America, sinking many tons of shipping with U-boats, German submarines. However, the development of the destroyer and aircraft with a longer patrol range were effective at countering the U-boat threat. By 1944, the Germans had lost the battle.

On June 6, 1944, the Western Allies finally launched the long awaited assault on "Fortress Europe" so wanted by Stalin. The offensive, codenamed Operation Overlord, began the early morning hours of June 6. The day, known as D-day, was marked by foul weather. Rommel, who was now in charge of defending France against possible Allied attack, thought the Allies would not attack during the stormy weather, and was on holiday in Germany. Besides this, the Germans were expecting an attack, but at the natural harbor of Calais and not the beaches of Normandy; a blunder that sealed the operation's success. They did not know about the Allies' artificial harbours, and clues planted by the Allies suggested Calais as the landing site.

By this time, the war was looking ever darker for Germany. On July 20, 1944, a group of conspiring German officers attempted to assassinate Hitler. The bomb they used did injure him, but the second was not used, and a table shielded Hitler in a stroke of luck. The plotters still could have launched a coup, but only the head of occupied Paris acted, arresting SS and Gestapo forces in the city. The German propaganda minister, Joseph Goebbels, rallied the Nazis, and saved the day for Hitler.

In France, the Allies took Normandy and finally Paris on August 25. In the east, the Russians had advanced almost to the former Polish-Russian border. At this time, Hitler introduced the V-weapons, the V-1 flying bomb and, later, the V-2, the first rockets used in modern warfare. The V-1 was often intercepted by air pilots, but the V-2 was extremely fast and carried a large payload. However, this advance came too late in the war to have any real effect. The Germans were also on the verge on introducing a number of terrifying new weapons, including advanced jet aircraft, which were too fast for ordinary propeller aircraft, and submarine improvements which would allow the Germans to again fight effectively in the Atlantic. All this came too late to save Hitler. Although a September invasion of The Netherlands failed, the Allies made steady advances. In the winter of 1944, Hitler put everything into one last desperate gamble in the West, known as the Battle of the Bulge, which, despite an initial advance, was a failure, because the introduction of new Allied tanks and low troop numbers among the Germans prevented any real action being taken.

In early February 1945, the three Allied leaders, Franklin Roosevelt, Winston Churchill, and Joseph Stalin, met at newly liberated Yalta in the Crimea in the Soviet Union in the Yalta Conference. Here, they agreed upon a plan to divide post-war Europe. Most of the east went to Stalin, who agreed to allow free elections in Eastern Europe, which he never did. The west went to Britain, France, and the U.S. Post-war Germany would be split between the four, as would Berlin. Here the territory of the Cold War was set. The boundaries of a new Europe, stripped of some of its oldest ruling families, were drawn up by the three men at Yalta.

At the beginning of 1945, Hitler was on his last strings. The Russians launched a devastating attack from Poland, where they had liberated Warsaw, into Germany and Eastern Europe, intending to take Berlin. The Germans collapsed in the West, allowing the Allies to fan out across Germany. However, the Supreme Allied Commander, American general Dwight D. Eisenhower, refused to strike for Berlin, and instead became obsessed with reports of possible guerrilla activity in southern Germany, which in reality existed only in the propaganda of Joseph Goebbels. By April 25, the Russians had besieged Berlin. Hitler remained in the city in a bunker under the Chancellery garden. On April 30, he committed suicide, after a ritual wedding with his long time mistress Eva Braun. The Germans held out another 7 days under Admiral Doenitz, their new leader, but the Germans surrendered unconditionally on May 7, 1945, ending the war in Europe (see V-E Day).

Rivalries that had begun during the war, combined with the sense of strength in the victorious powers, laid the foundations of the Iron Curtain and of the Cold War.

The war in the Pacific

The Holocaust

The Holocaust (which roughly means "great fire") was the deliberate, systematic, and horrific murder of millions of Jews and other minorities during World War II by the Nazi regime in Germany. Several differing views exist regarding whether it was intended to occur from the war's beginning, or if the plans for it came about later. Regardless, persecution of Jews extended well before the war even started, such as in the Kristallnacht (literally "Crystal Night", Night of Broken Glass). The Nazis used propaganda to great effect to stir up anti-Semitic feelings within ordinary Germans.

After the conquest of Poland, the Third Reich, which had previously deported Jews and other "undesirables", suddenly had within its borders the largest concentration of Jews in the world. The solution was to round up Jews and place them in concentration camps or in ghettos, cordoned off sections of cities where Jews were forced to live in deplorable conditions, often with tens of thousands starving to death, and the bodies decaying in the streets. As appalling as this sounds, they were the lucky ones. After the invasion of the Soviet Union, armed killing squads of SS men known as Einsatzgruppen systematically rounded up Jews and murdered an estimated one million Jews within the country. As barbaric and inhuman as this seems, it was too slow and inefficient by Nazi standards.

In 1942, the top leadership met in Wannsee, a suburb of Berlin, and began to plan a more efficient way to slaughter the Jews. The Nazis created a system of extermination camps throughout Poland, and began rounding up Jews from the Soviet Union, and from the Ghettos. Not only were Jews shot or gassed to death en masse, but they were forced to provide slave labor and they were used in horrific medical experiments (see Human experimentation in Nazi Germany). Out of the widespread condemnation of the Nazis' medical experiments, the Nuremberg Code of medical ethics was devised.

The Nazis took a sadistic pleasure in the death camps; the entrance to the worst camp, Auschwitz, stated "Arbeit Macht Frei"—"Work Makes Free". In the end, [six] million Jews, homosexuals, Jehovah's Witnesses, Gypsies and political prisoners were killed by various means, mainly in the death camps. An additional seven million Soviet and other Allied prisoners of war died in camps and holding areas.

There is some controversy over whether ordinary Germans knew about the Holocaust. It appears that many Germans knew about the concentration camps; such things were prominently displayed in magazines and newspapers. In many places, Jews had to walk past towns and villages on their way to work as slaves in German industry. In any case, Allied soldiers reported that the smell of the camps carried for miles. A very small number of people deny the Holocaust occurred entirely, though these claims have been routinely discredited by mainstream historians.

The Nuclear Age begins

During the 1930s, innovations in physics made it apparent that it could be possible to develop nuclear weapons of incredible power using nuclear reactions. When World War II broke out, scientists and advisors among the Allies feared that Nazi Germany may have been trying to develop its own atomic weapons, and the United States and the United Kingdom pooled their efforts in what became known as the Manhattan Project to beat them to it. At the secret Los Alamos laboratory in New Mexico, scientist Robert Oppenheimer led a team of the world's top scientists to develop the first nuclear weapons, the first of which was tested at the Trinity site in July 1945. However, Germany had surrendered in May 1945, and it had been discovered that the German atomic bomb program had not been very close to success.

The Allied team produced two nuclear weapons for use in the war, one powered by uranium-235 and the other by plutonium as fissionable material, named "Little Boy" and "Fat Man". These were dropped on the Japanese cities of Hiroshima and Nagasaki in August 1945. This, in combination with the Soviet entrance in the war, convinced the Japanese to surrender unconditionally. These two weapons remain the only two nuclear weapons ever used against other countries in war.

Nuclear weapons brought an entirely new and terrifying possibility to warfare: a nuclear holocaust. While at first the United States held a monopoly on the production of nuclear weapons, the Soviet Union, with some assistance from espionage, managed to detonate its first weapon (dubbed "Joe-1" by the West) in August 1949. The post-war relations between the two, which had already been deteriorating, began to rapidly disintegrate. Soon the two were locked in a massive stockpiling of nuclear weapons. The United States began a crash-program to develop the first hydrogen bomb in 1950, and detonated its first thermonuclear weapon in 1952. This new weapon was alone over 400 times as powerful as the weapons used against Japan. The Soviet Union detonated a primitive thermonuclear weapon in 1953 and a full-fledged one in 1955.

Since the 1940s there were concerns about the rising proliferation of nuclear weapons to new countries, which was seen as being destabilizing to international relations, spurring regional arms races, and generally increasing the likelihood of some form of nuclear war. Eventually, seven nations would overtly develop nuclear weapons, and still maintain stockpiles today: the United States, the Soviet Union (and later Russia would inherit these), the United Kingdom, France, China, India, and Pakistan. South Africa developed six crude weapons in the 1980s (which it later dismantled), and Israel almost certainly developed nuclear weapons though it never confirmed nor denied it. The creation of the Nuclear Non-proliferation Treaty in 1968 was an attempt to curtail such proliferation, but a number of countries developed nuclear weapons since it was signed (and many did not sign it), and a number of other countries, including Libya, Iran, and North Korea, were suspected of having clandestine nuclear weapons programs.

The post-war world

Following World War II, the majority of the industrialized world lay in ruins as a result of aerial bombings, naval bombardment, and protracted land campaigns. The United States was a notable exception to this; barring Pearl Harbor and some minor incidents, the U.S. had suffered no attacks upon its territory. The United States and the Soviet Union, which, despite the devastation of its most populated areas, rebuilt quickly, found themselves the world's two dominant superpowers.

Much of Western Europe was rebuilt after the war with assistance from the Marshall Plan. Germany, chief instigator of the war, was placed under joint military occupation by the United States, Great Britain, France, and the Soviet Union. Berlin, although in Soviet-controlled territory, was also divided among the four powers. Occupation of Berlin would continue until 1990. Japan was also placed under U.S. occupation, that would last five years, until 1949. Oddly, these two Axis powers, despite military occupation, soon rose to become the second (Japan) and third (West Germany) most powerful economies in the world.

The failure of the League of Nations to prevent World War II essentially discredited the organization, and it was dissolved. A new attempt at world peace was begun with the founding of the United Nations on October 24, 1945 in San Francisco. Today, nearly all countries are members, but despite its many successes, the organization's success at achieving its goal of world peace is dubious. The organization was never given enough power to overcome the conflicting interests and priorities of its member nations.

The end of empires: decolonization

Almost all of the major nations that were involved in World War II began shedding their overseas colonies soon after the conflict. In Africa, nationalists such as Jomo Kenyatta of Kenya and Kwame Nkrumah of Ghana led their respective nations to independence from foreign rule. The tactics employed by the revolutionaries ranged from non-violent forms of protest to armed rebellions, depending on the nation involved. The United States granted independence to the Philippines, its major Pacific possession. European powers also began withdrawing from their possessions in Africa and Asia. France was forced out of both Indochina and, later, Algeria.

Mutually assured destruction: the Cold War (1947–1991)

War by proxy

Two wars and a near-war in the 1950s became the foci for capitalist versus communist struggle. The first war was the Korean War, fought between People's Republic of China-backed North Korea and mainly United States-backed South Korea. North Korea's invasion of South Korea led to United Nations intervention. General Douglas MacArthur led troops from the United States, Canada, Australia, Great Britain, and other countries in repulsing the Northern invasion. However, the war reached a stalemate after Chinese intervention pushed U.N. forces back, and a cease-fire ended hostilities, leaving the two Koreas divided and tense for the rest of the century.

The second war, the Vietnam War, was perhaps the second most visible war of the 20th century, after World War II. After the French withdrawal from its former colony, Vietnam became partitioned into two halves, much like Korea. Fighting between North and South eventually escalated into a regional war. The United States provided aid to South Vietnam, but was not directly involved until the Gulf of Tonkin Resolution, passed in reaction to a supposed North Vietnamese attack upon American destroyers, brought the U.S. into the war as a belligerent. The war was initially viewed as a fight to contain communism (see containment, Truman Doctrine, and Domino Theory), but, as more Americans were drafted and news of events such as the Tet Offensive and My Lai massacre leaked out, American sentiment turned against the war. U.S. PresidentRichard Nixon was elected partially on claims of a "secret plan" to stop the war. This Nixon Doctrine involved a gradual pullout of American forces; South Vietnamese units were supposed to replace them, backed up by American air power. Unfortunately, the plan went awry, and the war spilled into neighboring Cambodia while South Vietnamese forces were pushed further back. Eventually, the U.S. and North Vietnam signed the Paris Peace Accords, ending U.S. involvement in the war. With the threat of U.S. retaliation gone, the North proceeded to violate the ceasefire and invaded the South with full military force. Saigon was captured on April 30, 1975, and Vietnam was unified under Communist rule a year later, effectively bringing an end to one of the most unpopular wars of all time.

The Cuban Missile Crisis illustrates just how close to the brink of nuclear war the world came during the Cold War. Cuba, under Fidel Castro's socialist government, had formed close ties with the Soviet Union. This was obviously disquieting to the United States, given Cuba's proximity. When Lockheed U-2 spy plane flights over the island revealed that Soviet missile launchers were being installed, U.S. PresidentJohn F. Kennedy instituted a naval blockade and publicly confronted the Soviet Union. After a tense week, the Soviet Union backed down and ordered the launchers removed, not wanting to risk igniting a new world war.

The space race

With Cold War tensions running high, the Soviet Union and United States took their rivalry to the stars in 1957 with the Soviet launch of Sputnik. A "space race" between the two powers followed. Although the USSR reached several important milestones, such as the first craft on the Moon (Luna 2) and the first human in space (Yuri Gagarin), the U.S. allegedly pulled ahead eventually with its Mercury, Gemini, and Apollo programs, which culminated in Apollo 11's manned landing on the moon. Five more manned landings followed (Apollo 13 was forced to abort its mission). Nevertheless, despite its successes U.S. space program couldn't match many major achievements of Soviet space program, such as unmanned rover-based space exploration and image and video transfer from surface of another planet, until early 21st century.

In later decades, space became a somewhat friendlier place. Regular manned space flights were made possible with the American space shuttle, which was the first reusable spacecraft to be successfully used. Mir and Skylab enabled prolonged human habitation in space. In the 1990s, work on the International Space Station began, and by the end of the century, while still incomplete, it was in continual use by astronauts from the United States, Europe, Russia, Japan, and Canada.

The end of the Cold War

By the 1980s, the Soviet Union was weakening. The Sino-Soviet split had removed the USSR's most powerful ally, the People's Republic of China. Its arms race with the U.S. was draining the country of funds, and further weakened by internal pressures, ethnic and political. Mikhail Gorbachev, its last leader, attempted to reform the country with glasnost and perestroika, but the formation of Solidarity, the fall of the Berlin Wall, and the breaking-off of several Soviet republics, such as Lithuania, started a slippery slope of events that culminated in a coup to overthrow Gorbachev, organized by Communist Party hard-liners. Boris Yeltsin, president of Russia, organized mass opposition, and the coup failed. On December 26, 1991, the Soviet Union was officially disbanded into its constituent republics, thus putting a final line under the already exhausted Cold War.

The invention of the word processor, spreadsheet and database greatly improved office productivity over the old paper, typewriter and filing cabinet methods. The economic advantage given to businesses led to economic efficiencies in computers themselves. Cost-effective CPUs led to thousands of industrial and home-brew computer designs, many of which became successful; a home-computer boom was led by the Apple II, the ZX80 and the Commodore PET.

IBM, seeking to embrace the microcomputer revolution, devised its IBM Personal Computer (PC). Crucially, IBM developed the PC from third-party components that were available on the open market. The only impediment to another company duplicating the system's architecture was the proprietary BIOS software. Other companies, starting with Compaq, reverse engineered the BIOS and released PC compatible computers that soon became the dominant architecture. Microsoft, which produced an operating system for the PC, rode this wave of popularity to become the world's leading software company.

Computers also became a usable platform for entertainment. Computer games were first developed by software programmers exercising their creativity on large systems at universities, but these efforts became commercially successful in arcade games such as Pong and Space Invaders. Once the home computer market was established, young programmers in their bedrooms became the core of a youthful games industry. In order to take advantage of advancing technology, games consoles were created. Like arcade systems, these machines had custom hardware designed to do game-oriented operations (such as sprites and parallax scrolling) in preference to general purpose computing tasks.

Computer networks appeared in two main styles; the local area network, linking computers in an office or school to each other, and the wide area network, linking the local area networks together. Initially, computers depended on the telephone networks to link to each other, spawning the Bulletin Board sub-culture. However, a DARPA project to create bomb-proof computer networks led to the creation of the Internet, a network of networks. The core of this network was the robust TCP/IPnetwork protocol. Thanks to efforts from Al Gore, the Internet grew beyond its military role when universities and commercial businesses were permitted to connect their networks to it. The main impetus for this was electronic mail, a far faster and convenient form of communication than conventional letter and memo distribution, and the File Transfer Protocol (FTP). However, the Internet remained largely unknown to the general public, who were used to Bulletin Boards and services like Compuserve and America Online. This changed when Tim Berners-Lee devised a simpler form of Vannevar Bush's hypertext, which he dubbed the World Wide Web. "The Web" suddenly changed the Internet into a printing press beyond the geographic boundaries of physical countries; it was termed "cyberspace". Anyone with a computer and an Internet connection could write pages in the simple HTML format and publish their thoughts to the world.

The Web's immense success also fueled the commercial use of the Internet. Convenient home shopping had been an element of "visions of the future" since the development of the telephone, but now the race was on to provide convenient, interactive consumerism. Companies trading through web sites became known as "dot coms", due to the ".com" suffix of commercial Internet addresses.

The world at the end of the century

By the end of the century, more technological advances had been made than in all of preceding history. Communications and information technology, transportation technology, and medical advances had radically altered daily lives. Europe appeared to be at a sustainable peace for the first time in recorded history. The people of the Indian subcontinent, a sixth of the world population at the end of the century, had attained an indigenous independence for the first time in centuries. China, an ancient nation comprising a fifth of the world population, was finally open to the world in a new and powerful synthesis of west and east, creating a new state after the near-complete destruction of the old cultural order. With the end of colonialism and the Cold War, nearly a billion people in Africa were left with truly independent new nation states, some cut from whole cloth, standing up after centuries of foreign domination.

The world was undergoing its second major period of globalization; the first, which started in the 18th century, having been terminated by World War I. Since the US was in a position of almost unchallenged domination, a major part of the process was Americanization. This led to anti-Western and anti-American feelings in parts of the world, especially the Middle East. The influence of China and India was also rising, as the world's largest populations, long marginalized by the West and by their own rulers, were rapidly integrating with the world economy.

However, several problems faced the world. The gap between rich and poor nations continued to widen. Some said that this problem could not be fixed, that there was a set amount of wealth and it could only be shared by so many. Others said that the powerful nations with large economies were not doing enough to help improve the rapidly evolving economies of the Third World. However, developing countries faced many challenges, including the scale of the task to be surmounted, rapidly growing populations, and the need to protect the environment, and the cost that goes along with it.

Terrorism, dictatorship, and the spread of nuclear weapons were other issues requiring attention. The world was still blighted by small-scale wars and other violent conflicts, fueled by competition over resources and by ethnic conflicts. Despots such as Kim Jong-il of North Korea continued to lead their nations toward the development of nuclear weapons.

Disease threatened to destabilize many regions of the world. New viruses such as SARS and West Nile continued to spread. In poor nations, malaria and other diseases affected the majority of the population. Millions were infected with HIV, the virus which causes AIDS. The virus was becoming an epidemic in southern Africa.

The geographic distribution of surface warming during the 21st century calculated by the HadCM3 climate model if a business as usual scenario is assumed for economic growth and greenhouse gas emissions. In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F).

Perhaps most importantly, it was speculated that in the long term, environmental problems threatened the planet's liveability. The most serious problem was global warming, which was predicted to frequently flood coastal areas, due to human-caused emission of greenhouse gases, particularly carbon dioxide produced by the burning of fossil fuels. This prompted many nations to negotiate and sign the Kyoto treaty, which set mandatory limits on carbon dioxide emissions.

The celebration of the end of the 20th century and the beginning of the 21st century was at New Year's 2000, January 1, 2000. Yet, historically speaking the century, according to calendar, ended at the end of 2000.

World population

A significant driver of many of the problems at the end of the 20th century was overpopulation. At the century's end, the global population was 6.1 billion and rising. There was some hope on this score, because the number of children per woman had been decreasing throughout the world, not only in the rich countries. In the long term, it was predicted that the population would probably reach a plateau of nine billion around 2050. However, it remained doubtful whether the planet had the long-term capacity to sustain such numbers.